The invention relates to couplings in general, and more particularly to improvements in axially and angularly yieldable toothed plug-in elastic couplings for transmission of torque between rotary driving and driven units. Still more particularly, the invention relates to improvements in couplings of the type disclosed in the commonly owned copending patent application Ser. No. 07/683,485.
The copending patent application describes a coupling wherein a driven element (e.g., a hub) has an annulus of external teeth (particularly spherical teeth) which can be moved into and out of mesh with the internal teeth of a receiving portion. The latter has a substantially washer-like flange member which can be fastened to the output element of a driving unit, a substantially sleeve-like member which is provided with the annulus of internal teeth, and an elastomeric connector which is vulcanized or otherwise secured to the two members and permits such members to perform (within limits) tilting, axial and/or angular movements relative to each other.
When the flange is affixed to a driving unit and the external teeth of the hub mate with the internal teeth of the sleeve-like member, the hub and the receiving portion define a chamber which is substantially sealed from the surrounding atmosphere and wherein the temperature is apt to rise to a value at which the elastomeric material of the connector is likely to be affected to thus shorten the useful life of the receiving portion. Nevertheless, couplings of the above outlined character have found acceptance in various branches of the industry because they permit rapid connection of a driven unit to, and rapid disconnection of the driven unit from, a rotary driving unit. In addition, such couplings can damp vibrations and/or other stray movements in actual use, they enable the input element of the driven unit to move axially of the output element of the driving unit, and they also permit tilting as well as certain angular movements of the input and output elements relative to each other.
The aforediscussed heating of the elastomeric connector between the connecting and sleeve-like members of the receiving portion is attributable primarily to the fulling action upon the elastomeric material when the connector undergoes deformation in actual use of the coupling. If the coupling is relatively small, the ventilating action of air which penetrates into the chamber between the flange and the driven element of the coupling by flowing between the mating internal and external teeth is likely to suffice to prevent overheating of the connector. However, the situation is quite different if the coupling is relatively large, i.e., the connector is then heated to a temperature which suffices to cause premature aging and destruction of the connector because the fulling action is so pronounced that the relatively small quantity of atmospheric air which penetrates into the chamber between the mating internal and external teeth cannot ensure adequate cooling of the connector.
Attempts to overcome the aforediscussed drawbacks of presently known axially and angularly yieldable plug-in toothed elastic couplings include the drilling of holes into the assembled flange in order to admit additional quantities of relatively cool atmospheric air. Such proposals have met with limited success, and the making of holes into a finished receiving portion necessitates additional treatment in a drilling or like machine which contributes to the initial cost of the coupling. The holes are intended to permit escape of hot air from the chamber between the flange and the driven element of the coupling.